Acoustical tile and method of manufacturing it



H. w. HEINE 2,825,420

ACOUSTICAL TILE AND METHOD OF MANUFACTURING IT March 4, 1958 Filed Nov. 10, 1954 Hen/ y M Heme BY ZQWQ/ hlli l,

ATTORNEY ACOUSTICAL TILE AND METHOD OF MANUFACTURING IT This invention relates to acoustical tiles and to methods of manufacturing them.

One of the objects of this invention is the provision of an acoustical tile which has a light porous structure and a cratered surface, the combination of which results in high sound absorbing efiicicncy.

Another object of the invention is the provision of a method of manufacturing such tile.

A further object of the invention is the provision of such tile and a method of manufacturing it in which the cratered surface is formed of a glazed material thereby increasing the structural strength of the tile pieces.

A still further object of the invention is the provision of such tile and of a method of manufacturing it in which the porous structure of the tile is internally reinforced with a glazed material at points underlying the surface craters.

A still further object of the invention is the provision of an all ceramic, washable, fireproof acoustical tile and a method of manufacturing it having the features referred to above.

These and other objects of the invention will appear more fully from the following description considered together with the accompanying drawing.

In the drawing:

Fig. 1 is a perspective view of an acoustical tile in accordance with this invention.

Fig. 2 is a cross sectional view along the line 22 of Fig. 1.

Fig. 3 is a cross sectional view similar to Fig. 2 of a tile piece at an intermediate stage of manufacture in accordance with one embodiment of the invention.

Fig. 4 is a view similar to Fig. 2 of a tile piece at an intermediate stage of manufacture in accordance with another embodiment of the invention.

The method of this invention in accordance with a first embodiment comprises, in general, the formation of a wet plastic mass of diatomaceous earth, a carbonaceous material, such as sawdust or any other organic media containing hydroxyl groups, particularly the alcohol, sugar and glycerol groups, or organic groups which are converted thereto under the action of steam, and a dispersion in a suitable vehicle of a glazing frit in addition to a substantial amount of water. The mass should preferably have as much water as it will hold and still permit it to retain a given shape.

The mass is thoroughly mixed and formed into blocks of desired shape and then fired in a kiln at a temperature in the burning range of the diatomaceous earth which will also be above the burning point of the carbonaceous material and below the fluxing point of the diatomaceous earth or of any other ceramic material which might be admixed therewith. A preferred range is about 1800 to 2200 F. although this range may be varied to suit the particular frits and auxiliary fiuxing agents to be used. Under these conditions, steam first evolves from the pieces due to the high water content, and then gases from the burning of the carbonaceous material. The evoluited States Patent 2,825,420 Patented Mar. 4, 1958 tion of the steam retards the formation of the gases so that the total time of evolution of both steam and gases is sulficient to permit a setting up of the block with sufficient rigidity to prevent them from collapsing and destroying the voids developed by the steam and gases. Also the steam is effective in releasing or forming volatile organic media from the carbonaceous material having terminal OH groups which are effective to polymerize to a limited extent the silica groups of the ceramic material to form silica carbide polymers which make the final product tough and handleable.

When the evolution of gases is completed or nearly completed, the frit material, for some reason which is not fully understood, exudes to the surfaces of the pieces and in accordance with a prior invention, described in my applications for patents, Serial No. 268,661, filed January 28, 1952 now Patent No. 2,681,865 and Serial No. 324,- 852, filed December 8, 1952 vitrifies on the surface of the tile pieces as a surface glaze, leaving the interior substantially free of or unaffected by the frit material. However, in accordance with this embodiment of the present invention, I apply an auxiliary fiuxing agent dispersed in a suitable vehicle to isolated areas on the surface of the tile pieces. The pieces are then fired in the kiln and after the evolution of the steam and gases, the frit exuding from the interior mixes with the auxiliary agent at these isolated areas and forms a eutectic which runs back into the porous interior of the pieces.

The auxiliary fluxing agent may be applied to the surface by spraying or otherwise to develop droplets thereof on the surface or other forms of isolated areas. In this Way the eutectic will be formed only at the localized or isolated areas over the surface corresponding to the drops of auxiliary fiuxing agent applied. The remainder of the surface surrounding these isolated areas will be covered with the frit exuding from the interior and will harden or vitrify and remain there as a permanent glaze finish. It will contain irregular craters at the places where the droplets were effectively mixed with the frit. At the same time, the interior porous structure of the tile underlying the craters will become reinforced with the fluxed frit without destroying the porous structure.

In accordance with a second embodiment of the invention, instead of adding the glazing frit to the wet mass in the beginning, a continuous layer of this glazing frit is applied to the surfaces of the pieces after they have been burned and the porous structure has been developed. The auxiliary fiuxing agent is then sprayed on top of the glazing frit after the glazing frit has become either dried or vitrified on the surface. The pieces are then heated to a temperature above the melting point of the auxiliary fiuxing agent and at the glazing temperature of the original frit, in the case Where the frit has merely been dried. In the case where the frit has been preglazed and the auxiliary fluxing agent subsequently applied, the kiln temperature is set below the glazing temperature of the original frit but above the melting point of the auxiliary fiuxing agent. The droplets of the auxiliary fiuxing agent coming into contact with the layer of the frit develops similar localized areas of a eutectic consisting of a mixture of the two which flows downwardly into the pores, leaving a similar cratered coating as in the case of the first embodiment and a similar reinforcement of the porous structure underlying the craters. Where the auxiliary fiuxing agent is applied to the dried frit before vitrification, heating is continued until the frit becomes vitrified.

Figs. 1 and 2 of the accompanying drawing illustrate the manufactured product of both embodiments, the numeral 11 designating the minutely porous base structure and 12 the cratered coating. The craters 13 of the coating are contiguous with the minute pores of the base structure and the latter are reinforced by the glazed frit and they are irregularly shaped and spaced which increases sound absorption efiiciency in contrast to prior types of acoustical tile having regularly spaced openings of geometrical shape, usually circular.

In Fig. 3 there is illustrated the condition of the pieces in accordance with the first embodiment after the auxiliary fluxing agent is sprayed thereon in droplets 15. The areas where these droplets fall will correspond to the craters 13 of the finished pieces.

In Fig. 4 there is illustrated the condition of the pieces in accordance with the second embodiment after the auxiliary fluxing agent is applied in droplets 16 over the glazing frit 17 in either a dry or glazed form, the latter being continuous. In this case, as in the first embodiment, the areas where these droplets 16 fall will correspond to the craters 13 of the finished pieces.

The glazing frit should soften and form a glaze at the firing temperature without becoming a running liquid. Examples of suitable frit compositions for this purpose and their softening temperatures are as follows:

Composition of glazing frits Feldspar 71.5, CaCO 8.6, clay 7.7 and flint l2.2 2070 Canadian spar 59.62, whiting 8.03, zinc oxide 6.50,

Florida kaolin 13.81 and flint 12.04 1976 CaO 47.5 and B 52.5 1958 The auxiliary fluxing agents should have a melting point below the softening point of the glazing frit, preferably in the range of about 700 to 1600 F. and mix therewith to form a running liquid. Examples of suitable auxiliary fluxing agents and their melting points are as follows:

Composition of auxiliary fluxirzg agents F. PbO 88.0 and S 12.0 990 K 0 55, SiO 45-- 1336 K 0 17.5 and $10 82.5 1616 K 0 17.4, $10 77.4 and A1 0 5.2 1607 N3 0 51.5 and $10 48.5 1526 N3 0 18.4 and $10 81.6 1580 Na O 17.5, s10 77.6 and A1 0 1472 B210 76.5 and B 0 23.5 1382 KzO-B203 and NflgO-BzOg PbO 60.8, A1 0 7.1 and S10 31.45 1212 F130 77.6, B 0 6.1 and $10 16.3 779 N3 0 24.2, B 0 35.2 and S10 40.6 1058 K 0 23.7, B 0 37.2 and $10 39.1 1211 Other suitable glazing frits and auxiliary fiuxing agents may be used, the above listed items being given merely by way of example and not by way of limitation.

The glazing frits and auxiliary fiuxing agents are dispersed as a solution or suspension in any suitable vehicle, such as water, alcohol, or mineral acid, or any other of the commonly used liquid vehicles, in which any of the usual opacifiers, such as ammonium carbonate, may be added.

I claim:

1. The method of manufacturing acoustical tile comprismg forming a wet plastic mixture of diatomaceous earth a carbonaceous material, and a dispersion of a glazing frit having a glazing temperature within the burning range of the diatomaceous earth, forming the mixture into pieces of desired shape, applying to isolated areas on the surface of the pieces a fiuxing agent capable of melting the int at said temperature, placing the pieces while in the wet state 111 a zone heated to the glazing temperature of the frit, and maintaining the pieces in the heated zone until the frit exudes to the surfaces of the pieces, vitrifies in the spaces surrounding said isolated areas, mixes with the fiuxing agent at said isolated areas to form a eutectic, and said eutectic flows into the interior of the pieces leaving a glazed cratered surface.

2. The method as defined by claim 1 in which the fluxing agent comprises 15 to of a member selected from the group consisting of Si0 and B 0 3. The method as defined by claim 2 in which the fluxing agent comprises also at least one member selected from the group consisting of K 0, Na O, BaO, PhD and A1 0 4. In a method for the manufacture of acoustic tiles having a glazed frit surface with open pores, the step of reinforcing the walls of said pores which consists in applying to isolated areas of the glazed frit at a temperature below its melting point, an agent capable of fluxing the glaze at said temperature, and permitting the glaze at the isolated areas to flux under the influence of the fluxing agent and flow into the interior of the pores of the tile.

5. The method as defined by claim 4 in which the fluxing agent comprises 15 to 85 of a member selected from the group consisting of SiO and B 0 6. The method as defined by claim 5 in which the fluxing agent comprises also at least one member selected from the group consisting of K 0, Na O, BaO, PbO and A1 0 7. The method of manufacturing acoustical tile, comprising forming a wet plastic mixture of diatomaceous earth, a carbonaceous material and a liquid dispersion of a glazing frit having a softening temperature in the range of about 1800 to 200 F., forming the mixture into pieces of desired shape, placing the pieces while in the Wet state in a zone heated to the softening temperature of the frit, applying to isolated areas on the surface of the pieces a fluxing agent having a melting point in the range of about 700 to 1600 F. and maintaining the pieces in the heated zone until the frit exudes to the surface of the pieces, vitrifies in the spaces surrounding the isolated areas, mixes with the fluxing agent at said isolated areas, and flows into the interior of the pieces leaving a glazed cratered surface.

8. The method as defined by claim 7 in which the fluxing agent comprises 15 to 85% of a member selected from the group consisting of SiO and B 0 9. The method as defined by claim 8 in which the fiuxing agent comprises also at least one member selected from the group consisting of K 0, Na O, BaO, PhD and A1 0 10. An acoustical tile having a porous ceramic core with a surface layer of glazed frit, and said surface layer having open pores 0r craters communicating with the pores of the tile core, and the walls of said pores or craters reinforced with a eutectic.

11. An acoustical tile having a porous ceramic core with a surface layer of glazed frit, and said surface layer having open pores or craters communicating with the pores of the tile core, and the walls of said pores or craters, and the tile core underlying the same reinforced with a eutectic.

12. In a method for the manufacture of acoustical tile having a glazed frit surface with open craters or pores, the steps of reinforcing the walls of said craters or pores with a eutectic, which consists in first applying to the glazed frit surface a fluxing agent capable of forming a eutectic with said surface glaze, and secondly, applying heat until the eutectic is formed and sufficient thereof flows into the craters or pores for wall reinforcement but retaining the desired acoustical properties of said tile.

13. The method as defined by claim 12, in which the fluxing agent comprises 15 to 85% of a member selected from the group consisting of SiO and B 0 14. The method as defined by claim 12 in which the 5 6 fluxing agent comprises also at least one member se- 265,076 Henderson Sept. 26, 1882 lected from the group consisting of K 0; N2 0, 13:10, 1,929,425 Hermann Oct. 10, 1933 PhD and A1 0 1,999,371 Parsons Apr. 30, 1935 2,627,101 Clercq Feb. 3, 1953 er c Cited in the l of this Patent 5 2,690,065 Harman et a1 Sept. 28, 1954 UNITED STATES PATENTS D. 168,763 Prisland Feb. 3, 1953 

10. AN ACOUSTICAL TILE HAVING A POROUS CERAMIC CORE WITH A SURFACE LAYER OF GLAZED FRIT, AND SAID SURFACE LAYER HAVING OPEN PORES OR CRATERS COMMUNICATING WITH THE PORES OF THE TILE CORE, AND THE WALLS OF SAID PORES OR CRATERS REINFORCED WITH A EUTECTIC.
 12. IN A METHOD FOR THE MANUFACTURE OF ACOUSTICAL TILE HAVING A GLAZED FRIT SURFACE WITH OPEN CRATERS OR PORES, THE STEPS OF REINFORCING THE WALLS OF SAID CRATERS OR PORES WITH A EUTECTIC, WHICH CONSISTS IN FIRST APPLYING TO THE GLAZED FRIT SURFACE A FLUXING AGENT CAPABLE OF FORMING A EUTECTIC WITH SAID SURFACE GLAZE, AND SECONDLY, APPLYING HEAT UNTIL THE EUTECTIC IS FORMED AND SUFFICIENT THEREOF FLOWS INTO THE CRATERS OR PORES FOR WALL REINFORCEMENT BUT RETAINING THE DESIRED ACOUSTICAL PROPERTIES OF SAID TILE. 